Molds & Tooling
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Melt Fracture Surface Defect of PEEK
Problem Phenomenon
During high-speed filling of PEEK, sharkskin-like or bamboo-node-like rough texture appears on the product surface; reducing speed improves it, but thin-wall parts then face the short shot contradiction.
Cause Analysis
When the melt passes through the gate or die lip, the shear rate exceeds the critical value and the surface melt fractures; PEEK's high viscosity makes the critical shear rate relatively low, so high-speed filling triggers it more easily.
Solution
①Use multi-stage injection — decelerate in the gate area and accelerate in the filling area; ②Enlarge the gate to reduce the shear rate; ③Appropriately raise the melt temperature to lower the viscosity; ④Switch to a lower-viscosity grade if necessary.
Key Takeaway
The core of PEEK melt fracture treatment is local shear rate control; multi-stage injection is the standard means to balance filling and surface quality; gate size is the key design variable.
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